As a photoreceptor used for electrophotography, commonly known is a photoreceptor in which a photoreceptor employing a photosensitive layer containing an inorganic photoconductive material or an organic photoconductive material is provided on a plate-shaped, a belt-shaped, or a drum-shaped aluminum support.
Electrophotographic performance of the above photoreceptor is largely influenced by the surface condition of an aluminum support as well as the photoreceptor.
When unevenness and scratches occur on the support surface because of insufficient mechanical smoothness, electrical defects, for example, are generated, whereby black spots, black streaks and such are observed. Thus, a mirror-finished process is usually carried out by a diamond tool and so forth. It is commonly known that Mg, Fe, Si, Cu, and Mn are also contained as an alloy composition to obtain desired mechanical strength of an aluminum support. In the case of an alloy component such as Fe or Si, however, not only a number of thin crystallizing materials are formed in the process of support treatment conducted by extrusion molding or drawing molding, but an aluminum melt tends to be formed around these crystallizing materials, via formation of an aluminum alloy. When a photosensitive layer is provided on those crystallizing materials and the aluminum melt around them to form images, image defects tend to be generated.
It is proposed, for example, that the amount of Fe component is not more than 0.2% by weight, and that of Si component is not more than 0.1% by weight (Refer to Patent Document 1, for example.). It is also proposed that a diameter and an area ratio of the crystallizing material are not more than 3 μm and not more than 0.5% (Refer to Patent Document 2, for example.).
However, it was difficult to obtain a high quality toner image, even though the amount of the alloy component, and the diameter and the area ratio of the crystallizing material are specified.
Commonly known is a technique in which various defects on an aluminum support are covered, and an intermediate layer containing polyamide resin, vinyl acetate, or such is provided for the purpose of adjusting an image obtained when the technique is used for a photoreceptor (Refer to Patent Document 3, for example.).
In the case of a photoreceptor in which the above intermediate layer is provided, however, though a problem originated from defects on the support is solved, there is another problem causing image deterioration via increased residual potential and a lowered charging and charge retention property, since fatigue and degradation of images occur easily in the process of forming images repeatedly.
Proposed is a photoreceptor in which a hydrated aluminum oxide layer is also provided on an aluminum support, and a photosensitive layer containing a charge generation material and a charge transfer material is provided thereon (Refer to Patent Document 4, for example.). It is described that the foregoing hydrated aluminum oxide layer is also formed via pure water treatment approximately at 100° C., for example, and high sensitivity, excellent charging and charge maintaining properties, and repeating characteristics can be added to a photoreceptor via simple and easy hydrated processes and rectifying characteristics.
In the case of the photoreceptor employing an aluminum support having the foregoing hydrated aluminum oxide layer thereon, however, occurrence of image defects such as black spots and the like was observed under heavy-duty conditions (30° C. and 80% RH or 10° C. and 20% RH, for example), or during repeated use, when an image was formed by a reversal development method, contrary to an excellent property possessed in view of electrophotographic performance as described above. In the case of a copy machine or a printer employing laser light, for example, there was a problem that fog or density unevenness caused by a group of black spots was observed, though spot image exposure was conducted on a photoreceptor, a dot electrostatic image was formed, to conduct an image formation process by developing this via a reversal development method.
An electrophotographic photoreceptor in which a hydrated aluminum oxide alloy layer is provided on the surface of an electrically conductive support containing an aluminum alloy, and a photosensitive layer is provided thereon, wherein a diameter of crystallizing material particles contained in the aluminum alloy on the surface of the foregoing electrically conductive support is not more than 5 μm, and an area ratio occupied by the foregoing crystallizing material particles, based on the aluminum alloy on the surface of the foregoing electrically conductive support, is not more than 2% (Refer to Patent Document 5, for example.).
But, There was another problem that black spots were generated when a toner image was formed at high temperature and high humidity (30° C. and 80% RH, for example).
It is disclosed that a subbing layer (an intermediate layer) is provided in a photographic photoreceptor to control electrical conductivity between an electrically conductive support and a photosensitive layer, and also to enhance an adhesive power between an electrically conductive support and a charge generation layer. The charge generation layer and the charge transfer layer tend to be peeled off from the layer ends. To solve this problem, a method for forming a photoreceptor is described so as to provide the end of a photosensitive layer to the inward side of the end of an intermediate layer (Refer to Patent Document 6, for example.).
In the case of employing a subbing layer containing titanium oxide particles and such, for example, there is a problem that particles on the surface of a subbing layer are removed via abrasion of the subbing layer during image formation since the subbing layer is exposed, so that the surface of a electrophotographic photoreceptor is contaminated. Further, it is also seen as a problem that black spots are generated in the images of such a photoreceptor during image formation. There is also a problem that a toner adheres easily to the subbing layer during image formation, and it is difficult to clean up the attached toner, so that the toner is deposited at the end portion, whereby fog caused by insufficient toner cleaning is generated.
In relation to the photoreceptor in which an intermediate layer (a subbing layer) containing particles and a photosensitive layer are laminated on a support in this order, it has been investigated that removal of the particles from the intermediate layer is inhibited by covering the intermediate layer with the photosensitive layer, electrical conductivity is controlled via the intermediate layer, and adhesiveness is maintained. It is described that removal of particles (titanium oxide particles, for example) can be inhibited, maintaining the electrical conductivity control via an intermediate layer and adhesiveness, when titanium oxide is specifically employed for particles, and titanium oxide surface-treated by an organic silicon compound and an intermediate layer containing polyamide are used (Refer to Patent Document 7, for example.).
The coated layer end of a photosensitive layer, however, is peeled off during a lot of printing because of insufficient adhesion between a support and the photosensitive layer at the end of the coated layer, since the above resulting photoreceptor, in which an intermediate layer is covered by a photosensitive layer, has a layer structure having the photosensitive layer directly provided on a support, and coated film peeling adversely affect a cleaning capability property as well as development, whereby good quality images can not be obtained.
(Patent Document 1) Japanese Patent O.P.I. Publication No. 64-79339
(Patent Document 2) Japanese Patent O.P.I. Publication No. 1-285953
(Patent Document 3) Japanese Patent O.P.I. Publication No. 2003-345050
(Patent Document 4) Japanese Patent O.P.I. Publication No. 64-29852
(Patent Document 5) Japanese Patent O.P.I. Publication No. 6-3845
(Patent Document 6) Japanese Patent O.P.I. Publication No. 59-184359
(Patent Document 7) Japanese Patent O.P.I. Publication No. 2002-107986